The present invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. Specifically, the remote center positioner is useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the patient's abdominal wall.
In standard laparoscopic abdominal surgery, the patient's abdomen is insufflated with gas, and cannulas are passed through small (approximately 1/2 inch) incisions to provide entry ports for laparoscopic surgical instruments. The laparoscopic surgical instruments generally include an laparoscope for viewing the surgical field, and working tools such as clamps, graspers, scissors, staplers, and needle holders. The working tools are similar to those used in conventional (open) surgery, except that the working end of each tool is separated from its handle by an approximately 12-inch long extension tube. To perform surgical procedures the surgeon passes instruments through the cannulas and manipulates them inside the abdomen by sliding them in and out through the cannulas, rotating them in the cannulas, and "levering" (pivoting) them around centers of rotation approximately defined by the incisions in the muscles of the abdominal wall. The abdominal incisions do not provide stable reference positions or points of rotation, and so in order to maintain accurate positional control of an instrument during manipulation, the surgeon may need to manually constrain it to pivot around a fixed point coincident with the incision. Manual support of the pivot point is particularly important when the surgeon manipulates laparoscopes or other heavy instruments. Mechanical clamping devices are used to support the instruments in fixed orientations, but these devices do not provide a remote center of rotation for positioning the instruments.
In robotically assisted and telerobotic laparoscopic abdominal surgery the position of the surgical instruments is controlled by servo motors rather than directly by hand or with fixed clamps. With servo control, a means must be provided to ensure that the surgical instrument is constrained to move around a fixed center of rotation coincident with an entry incision in the patient's abdominal wall. Any other types of motion such as translation or rotation about other centers could cause patient injury.
Heretofore, there have been mechanisms directed to providing assistance in surgery. Thus, U.S. Pat. No. 4,756,655 to Jameson is directed to a manipulating mechanism having a control handle adapted to be positioned freely in three dimensions, a fixture for supporting a tool to be positioned, a linkage system which causes the end of the tool to move in the same direction as the control handle and a support structure. The linkage system includes a first linkage connected between the control handle and an effective ball-and-socket joint and a second linkage connected between the effective ball and socket joint and the fixture. Each linkage includes four link members rotatably connected in a parallelogram and a gimbal connected to one of the link members for mounting the linkage from the support structure.
The linkage system includes a first linkage connected between the control handle and a joint and a second linkage connected between the first linkage and the fixture. In the preferred embodiments, the linkage system is comprised of two motion translation mechanisms connected in series through an effective ball-and-socket joint, where each translation mechanism is essentially a pantograph adapted for rotation with respect to the support structure about two perpendicular axes. The motion of the control handle induces oppositely (or similarly, depending on the embodiment) directed motion of the ball-and-socket joint by means of one translation mechanism which in turn causes similarly directed motion of the tool by means of the second translation mechanism so that the motion of the tool is in the same direction as the motion of the control handle. The linkage system is directed to a master reflection system controlling a slave reflection mechanism and does not provide a remote center of spherical rotation.
U.S. Pat. No. 4,143,652 to Meier and Dbaly discloses a surgical retaining device for holding a surgical instrument in place, typically with hooks. The device includes a holder block for displaceably securing the surgical retaining device at a stationary object and at least one insert element into which there can be inserted and fixedly clamped the surgical instrument. Between the insert element and the holder block there is arranged a double-arm pivotable stand possessing an intermediate pin joint. The pivotable stand is connected at one end by means of a ball-and-socket joint at the insert element and at its other end by means of a further ball-and-socket joint with an overhang arm which can be fixedly clamped at random elevational and angular positions with respect to the holder block at the latter.
A paper given at the IEEE Engineering in Medicine and Biology Society 11th Annual International Conference in 1989 entitled SMOS: Stereotaxical Microtelemanipulator for Ocular Surgery shows a structure for use in ocular vitrectomy, and other medical fields such as radial keratotomy and plastic surgery. FIGS. 2 and 3 of the paper shows the mechanical structure of the SMOS. A carrier holds a rotatably mounted curved wrist. An instrument holder is movably mounted to the wrist for carrying an instrument or needle for working in the eye keeping the needle centered on the entrance aperture. This is described as realized in spherical coordinates in a reference whose zero point is the entrance aperture A. The mechanism creating these movements, which are in themselves the main actions of the vitrectomy operation, is called the wrist of the microtelemanipulator.
An article entitled "Robotic Surgery" in the March 1993 issue of IEEE Engineering in Medicine and Biology shows a motorized frame (FIG. 8) for use in prostate surgery. FIG. 8 shows a schematic layout of the main mechanical components of the device called SARP. The working envelope is small and can be flexibly constrained using mechanical stops to improve safety. The envelope is approximately the frustum of a cone. Several cones may be needed, depending on the size of the prostate, to remove the unwanted enlarged tissue from within the prostate.
The manual frame can only produce conical cavities because it is manually driven. However, the motorized frame is capable of producing both conical and barrel shape cavities. As a start, conical cavities are advocated to avoid moving along more than one axis at a time. Conical cavities are easy to produce using hot loop electrosurgery. Similar to the manual frame, a ring shape frame fitted with a diametrical arch is a carriage that carries the resectoscope. A C-shaped bracket fixed to the resectoscope helps ease the introduction of the motorized frame to the resectoscope. The axes are designed to be driven by motors. Back driving is possible when the servo action is disabled. Successive cuts are made by extending and retracting the cutting loop repeatedly and turning on the cutting current at the return stroke of the cutter. The ring moves to a new position for each cut. Several conical cavities can be resected from the prostate to relieve blockage. To achieve one or more of these conical cavities inside the prostate, the frame is fixed to a head travel so that it can move axially along the rotation axis of the ring axis.
None of the above-mentioned devices provide a light weight simple apparatus for providing a remote center of rotation for use in surgery with minimal obstruction of the surgical field as is disclosed and claimed herein.